A. Field
The invention relates to a clamping module for an internal pipe aligning and clamping apparatus for pipe sections to be welded, commonly referred to as a pipe line-up device.
B. Related Art
Pipe line-up devices and systems are used to internally align and clamp large pipe sections having ends prepared for butt welding so that the pipes are aligned concentrically end-to-end before the start of welding the pipe ends together. Such pipe line-up devices hold the pipe sections in alignment from inside the pipe sections during the welding procedure and then are controlled to release the pipe sections when the weld operation is completed. The welded sections are then moved away from the line-up device and a new prepared pipe section is moved into place for the next weld. Such line-up devices are familiar in continuous pipe laying operations where pipe sections of given length are butt welded end-to-end in a continuous operation to produce a continuous welded pipeline. The line-up devices are configured to operate from inside the pipe sections.
Exemplary known pipe line-up systems of this kind are described in U.S. Pat. No. 3,044,431 to Cummings; U.S. Pat. No. 3,387,761 to Pickard; U.S. Pat. No. 3,425,614 to Clark; U.S. Pat. No. 4,140,262 to Wilson et al.; U.S. Pat. No. 5,288,005 to Beakley et al.; U.S. Pat. No. 5,535,938 to Leduc; U.S. Pat. No. 5,597,108 to Dierlam; and U.S. Pat. No. 6,915,943 to Laing.
In such exemplary systems, a substantially self-contained pipe aligning and clamping system may include an arrangement of a frame, a power supply, piston actuators, a fluid pressure source, and a clamping module that includes two axially spaced sets of radially extendable clamping feet circumferentially spaced around the module, with a set of circumferentially spaced weld shoes between the clamping feet sets. The weld shoes typically are copper or other conductive metal elements that serve as anodes or cathodes for electrical welding operations on the pipe sections, and otherwise support the rear weld area. Other components suited to maneuver the line-up clamping apparatus in the pipe sections being welded may be provided, including a self-propelling drive systems and the like.
In use, the frame and associated apparatus including the clamping module are placed inside the first two pipe sections that have prepared ends to be butt welded together with the prepared ends facing each other end-to-end with the clamping module located so that one set of the clamping feet is located inside one pipe section on one side of the weld area where the pipe ends are to be butt welded together and the other set is located on the other side of the weld area in the other pipe section, and with the weld shoes located internally of and spanning the inner face of the weld area.
The clamping feet are then radially expanded by, typically, fluid or mechanical forces that may be generated by a suitable power source to align the pipe ends concentrically and support the weld area from the inner diameter of the pipe sections, while the weld shoes are extended to engage the rear side of the weld area between the pipe sections. The clamping feet sets may be sequentially extended or refracted in one pipe section and then in the other pipe section, or both may be actuated together. In typical systems, the radial forces driving the clamping feet of the clamping module are generated by fluid pressure acting on pistons or driving heads that axially drive mechanical linkages that convert the driving head axial motion to radial motion of the clamping feet. The clamping feet in turn force the pipe ends into concentric relationship, possibly rounding out any minor pipe eccentricity, and into alignment with the central axis of the aligned pipe sections. Various type welding operations may then be conducted to weld the pipe ends together from the outside of the pipe sections, with the weld shoes contacting the pipe ends during welding, possibly functioning as anodes or cathodes if electrical arc welding is used.
After the first two pipe sections are welded, the clamping feet and weld shoes are refracted, and the entire line-up system with the clamping module is either moved axially to the next weld area or the welded pipe sections are moved longitudinally until the line-up system is located at the next weld area between the free front end of the last pipe section that was welded and the rear end of the next pipe section to be welded. The aligning, clamping and welding process is then repeated to continuously assemble, align and weld pipe sections together to form a continuous pipeline.
In the typical known pipe line-up systems, the mechanical linkage arrangements used in clamping modules to drive the clamping feet radially are able to generate a limited amount of force in reaction to the axial piston or driving head driving forces, and tend to require careful maintenance because of their environment and the high forces involved in their operation. Moreover, the available ratio of axial movement of the piston or driving heads relative to the available degree of radial movement of the clamping feet limits the leverage available between the axially moving driving heads and the radially moving clamping feet, so that the forces generated in the clamping feet may be limited to less than what is desired.
A more robust and powerful clamping module for converting the axial driving head motion into radial clamping feet motion, preferably with force amplification, thus is highly desirable in pipe line-up systems of the type described above.